IBM ThinkPad Butterfly keyboard
The TrackWrite, also known as the butterfly keyboard, is a foldout laptop computer keyboard designed by John Karidis for IBM as part of the ThinkPad 701 series, released in 1995. It allowed the 701 series to be both compact (when closed) and comfortable to use (when open), despite being just 24.6 cm (9.7 in) wide with a 26.4 cm (10.4 in) VGA LCD. The 701 was the top selling laptop of 1995; however, as later laptop models featured progressively larger screens, the need for a folding keyboard was eliminated. Consequently, no model but the 701 used the butterfly keyboard.
The butterfly keyboard is split into two roughly triangular pieces that slide as the laptop's lid is opened or closed. As the lid is opened both pieces slide out to the sides, followed by one piece sliding downward. The two halves mesh to form a keyboard 29.2 cm (11.5 in) wide which overhangs the sides of the laptop body. Conversely, as the lid is closed one piece slides back, then both slide inward until the keyboard can be covered by the lid. The movement of the keyboard is driven by a cam on the lid's hinge, so the motions of the keyboard parts are always synchronized with the movement of the lid.